fuel return line questions

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Apr 10, 2003 | 07:32 PM

cjben

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Lead Driver

Joined: Apr 2001

Posts: 6,335

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From: Midwest

fuel return line questions

as many of u may remember, I have swapped a 1986 351w HO in place of my 302 in my 1978 f100.....here is my question/problem. The carb on the 351w is a 4 barrel, the one on the 302 was a 2 barrel. the 4 barrel has one line in the front and one in the back of the carb that look like they could be for fuel return lines. the 2 barrel had no fuel return line or a place for one. do I need fuel return lines? I have had the truck running in the garage, and up and down the alley a couple times, but not out on the road yet. i have not seen where there is any fuel coming out of these lines. If I need these lines, how hard would they be to run and make holes in the tank for them? thanks yet again, Ben

Apr 10, 2003 | 07:39 PM

RobSt

New User

Joined: Apr 2003

Posts: 8

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From: TX

fuel return line questions

on my 4 barrol edelbrock carb the one in back is th break vacume and the front bottom middle is pcv line and beside that is the vacume advance.

Apr 10, 2003 | 09:25 PM

220k-f-150

Senior User

Joined: Apr 2003

Posts: 243

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fuel return line questions

cjben,
The two hoses are part of fuel evaporative emission control system. I'm not sure, but I think your 78 had this. If your 78 came with a "charcoal canister" it had it.
Since you now have 4bbl. (2 fuel bowls) you need 2 "charcoal canisters".
Heres the routing.
Hose from carb. to a vacuum purge valve, with a one- way valve inbetween.
Purge valve to "charcoal Canister".
If possible, you could steal this from the vehicle you got your motor from.
I hope this helps.

Or leave it loose and hope that no fuel comes out when a float or needle and seat go bad inside carb.